The present invention relates to a system for regulating the pressure in a container with the aid of a vacuum pump which is connected to the container by means of a membrane pressure regulator equipped with a reference pressure chamber. The invention also relates to a method of regulating the container pressure with a system of this type.
It is often necessary to keep a constant pressure in a container (e.g. a vacuum chamber or processing chamber) in which, for example, a vapor-deposition, etching or drying process or the like takes place or to adapt the pressure in a certain manner to the process taking place in the container.
For example, it is known from East German Pat. No. 81,252 to keep the pressure in a vacuum system constant by intermittently opening servo-controlled needle valves. It is further known from this document to switch in or out additional vacuum pumps or to provide a choke flap in the suction line to enlarge or decrease the suction cross section. Finally, this document describes the regulation of the number of pumping revolutions of a rotating pump. It is difficult to properly dimension methods and apparatus of this type, and their dynamic characteristics, in particularly, pose problems.
German Offenlegungsschrift [laid-open patent application] No. 3,215,972 discloses a membrane pressure regulator which is disposed between the container and the vacuum pump and which serves the purpose of keeping a constant pressure within the container. For this purpose, a reference pressure chamber is accommodated in the pressure regulator housing, with one side of this chamber being formed by a membrane. The membrane serves as a setting member for the connection between the container and the vacuum pump. If the pressure in the reference pressure chamber corresponds to the pressure in the container, the connection between container and vacuum chamber is closed. If the pressure in the container increases, the membrane establishes a connection between the container and the vacuum pump. Membrane pressure regulators of this type can be used in a pressure range from 10 to 1000 mbar. Due to their very non-problematic dynamic behavior, having not tendency to vibrate over the entire pressure range, these membrane pressure regulators are particularly suitable to maintain a constant pressure in a container. By changing the reference pressure, regulators of this type can also be used, in principle, for pressure regulation in the container.